Explanation of what is a Solar Cell from Wikipedia Encyclopedia:

A solar cell is a semiconductor device that converts photons from the sun (solar light) into electricity. The general term for a solar cell including both solar and non-solar sources of light (such as photons from incandescent bulbs) is termed a photovoltaic cell. Fundamentally, the device needs to fulfill only two functions: photo-generation of charge carriers (electrons and holes) in a light-absorbing material, and separation of the charge carriers to a conductive contact that will transmit the electricity. This conversion is called the photovoltaic effect, and the field of research related to solar cells is known as photovoltaic.

The most common configuration of this device, the first generation photovoltaic, consists of a large-area, single layer p-n junctiondiode, which is capable of generating usable electricalenergy from light sources with the wavelengths of solar light. These cells are typically made using silicon. However, successive generations of photovoltaic cells are currently being developed that may improve the photo-conversion efficiency for future photovoltaic. The second generation of photovoltaic materials is based on multiple layers of p-n junction diodes. Each layer is designed to absorb a successively longer wavelength of light (lower energy), thus absorbing more of the solar spectrum and increasing the amount of electrical energy produced. The third generation of photovoltaic is very different from the other two, and is broadly defined as a semiconductor device which does not rely on a traditional p-n junction to separate photo-generated charge carriers. These new devices include dye sensitized cells, organic polymer cells, and quantum dot solar cells.

Solar cells have many applications. They are particularly well suited to, and historically used in, situations where electrical power from the grid is unavailable, such as in remote area power systems, Earth orbiting satellites, handheld calculators, remote radiotelephones and water pumping applications. Assemblies of solar cells (in the form of modules or solar panels) on building roofs can be connected through an inverter to the electricity grid in a net metering arrangement.